linux-kernel - Re: [PATCH 2/2] riscv, bpf: use lw when reading int cpu in bpf_get_smp_processor

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Message-ID: <deec25f9-9e58-4650-8920-eddd9995c28b@huawei.com>
Date: Sat, 16 Aug 2025 09:30:51 +0800
From: Pu Lehui <pulehui@...wei.com>
To: Radim Krčmář <rkrcmar@...tanamicro.com>,
	<bpf@...r.kernel.org>
CC: <stable@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>, Daniel
 Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, Martin
 KaFai Lau <martin.lau@...ux.dev>, Eduard Zingerman <eddyz87@...il.com>, Song
 Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>, John
 Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, Jiri Olsa
	<jolsa@...nel.org>, Björn Töpel <bjorn@...nel.org>,
	Puranjay Mohan <puranjay@...nel.org>, Paul Walmsley
	<paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, Albert Ou
	<aou@...s.berkeley.edu>, Alexandre Ghiti <alex@...ti.fr>, Kumar Kartikeya
 Dwivedi <memxor@...il.com>, <linux-riscv@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] riscv, bpf: use lw when reading int cpu in
 bpf_get_smp_processor_id



On 2025/8/12 17:02, Radim Krčmář wrote:
> emit_ld is wrong, because thread_info.cpu is 32-bit, not xlen-bit wide.
> The struct currently has a hole after cpu, so little endian accesses
> seemed fine.
> 
> Fixes: 2ddec2c80b44 ("riscv, bpf: inline bpf_get_smp_processor_id()")
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Radim Krčmář <rkrcmar@...tanamicro.com>
> ---
>   arch/riscv/net/bpf_jit_comp64.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
> index 6e1554d89681..9883a55d61b5 100644
> --- a/arch/riscv/net/bpf_jit_comp64.c
> +++ b/arch/riscv/net/bpf_jit_comp64.c
> @@ -1763,7 +1763,7 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>   		 */
>   		if (insn->src_reg == 0 && insn->imm == BPF_FUNC_get_smp_processor_id) {
>   			/* Load current CPU number in R0 */
> -			emit_ld(bpf_to_rv_reg(BPF_REG_0, ctx), offsetof(struct thread_info, cpu),
> +			emit_lw(bpf_to_rv_reg(BPF_REG_0, ctx), offsetof(struct thread_info, cpu),
>   				RV_REG_TP, ctx);
>   			break;
>   		}

Reviewed-by: Pu Lehui <pulehui@...wei.com>